What is the point of having different engine cycles?

In summary, the Otto cycle, Carnot cycle, and Diesel cycle are all different types of thermodynamic cycles used in internal combustion engines. They differ in their compression and power strokes, as well as their ignition and exhaust strokes. The Otto cycle, used in gasoline engines, has a limit on compression due to the possibility of self-ignition. This can be improved by using a high-octane fuel, but it is more expensive. The diesel engine, on the other hand, can use higher compression levels and cheaper, less refined fuel, making it more efficient. The Carnot cycle is an ideal cycle that shows the maximum efficiency that can be achieved.
  • #1
JustinLiang
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For example, what is the difference between Otto cycle, Carnot cycle, Diesel cycle other than that they have different compression/power strokes and ignition/exhaustion strokes?
 
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  • #2
In order to improve the efficiency of the Otto cycle one must increase the compression ratio of an internal-combustion engine. However, in the gasoline engine there is a limit – the gasoline-air mixture will self ignite once the compression gets too high (because every compression drives temperature increase). So, either you can have a low-efficient, low-compression engine that uses a cheap fuel, or you can have a high-efficient, high-compression engine that uses expensive, high-refined fuel that won't self-ignite even at high compression levels (a 120 octane gasoline?).

In diesel engine this problem is solved. The diesel engine can use much higher compression levels than the gasoline engine reaching higher efficiency. In addition, the diesel engine can use fuel that is not nearly as refined as the high-octane gasoline fuel (thus cheaper).

Of course the Carnot cycle is an ideal cycle and indicates the upper value of achievable performance.
 

Related to What is the point of having different engine cycles?

1. What are the different engine cycles and why do they matter?

The four main engine cycles are the Otto cycle, Diesel cycle, Atkinson cycle, and Miller cycle. These cycles refer to the thermodynamic processes that occur within an engine to convert fuel into energy. Each cycle has its own advantages and disadvantages, and the choice of cycle depends on the application and efficiency goals of the engine.

2. How do these engine cycles differ from each other?

The main difference between these cycles is the combustion process. In the Otto cycle, the fuel is ignited by a spark plug, while in the Diesel cycle, the fuel is ignited by the heat of compressed air. The Atkinson cycle has a longer expansion stroke, leading to higher fuel efficiency, while the Miller cycle has a shorter compression stroke, leading to lower emissions.

3. Which engine cycle is the most efficient?

It is difficult to determine which engine cycle is the most efficient, as it depends on the specific application and efficiency goals. However, the Atkinson cycle is generally considered to be the most fuel-efficient, while the Miller cycle is known for its low emissions. Ultimately, the most efficient cycle is one that is designed and optimized for a specific purpose.

4. What are the advantages of having different engine cycles?

Having different engine cycles allows for flexibility and customization in engine design. It allows engineers to choose the most suitable cycle for a specific application, whether it be for fuel efficiency, power, or emissions control. Having a variety of engine cycles also promotes innovation and competition in the automotive industry.

5. Is there a future for new engine cycles?

Yes, there is always room for improvement and innovation in engine design. In fact, there are already new engine cycles being developed, such as the Brayton cycle and the Rankine cycle, which use different working fluids and processes to achieve greater efficiency. With advancements in technology and a focus on sustainability, we can expect to see new engine cycles being developed and integrated into future vehicles.

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